TrotterBob
100 W
So what happens to .25mm copper busbars after a few months when the copper starts to corrode? Does it lose any conductivity?
Spot Welding Copper Strips to 18650 Battery Cells
- Thread starter mkp007
- Start date
garolittle
10 kW
TrotterBob said:
No
Depends on the environment and degree of exposure.
Tin plating, "tinning" copper is certainly required for long term integrity in coastal areas with salt fog atmospheres
unless the case is very well sealed.
Of course rising resistance may not be a big problem over just a few years, if the conductivity was overkill for that use case anyway.
Tin plating, "tinning" copper is certainly required for long term integrity in coastal areas with salt fog atmospheres
unless the case is very well sealed.
Of course rising resistance may not be a big problem over just a few years, if the conductivity was overkill for that use case anyway.
ridethelightning
1 MW
- Joined
- Jul 21, 2013
- Messages
- 2,010
anyone able to recommend a good source of tin for plating copper?
id like to try it as i suspect it may work better than nickel when it comes to welding
id like to try it as i suspect it may work better than nickel when it comes to welding
spinningmagnets
100 TW
The shells of 18650/21700 cells are typically a steel core with nickel-plating for corrosion resistance.
The cathode positive nipple on "some" Tesla 21700's are aluminum with no nickel-plating. Tesla uses ultrasonic vibrations to friction-weld aluminum fuse-wire to the cell.
The cathode positive nipple on "some" Tesla 21700's are aluminum with no nickel-plating. Tesla uses ultrasonic vibrations to friction-weld aluminum fuse-wire to the cell.
So...I was thinking about the core task to be performed in making the parallel and series connections.
And it's not welding, soldering or any particular technology.
It's making a low resistance, chemically stable, vibration resistant connection by whatever means works.
So I thought of a couple alternatives:
1> Flip it - from what I understand (my welder is due for delivery today) while welding copper to nickel is a challenge, welding nickel to copper is trivial.
So if you're using cell holders, and your arrangement is symmetrical or mostly symmetrical, you could lay out your nickel parallel strips using the empty holders as a template, then lay your copper series strips with a slot or notch cut out, and weld the copper to the nickel.
Once the sheet is welded up, assemble the cells in the holders, flip the sheet and lay it on top and weld through the holes/notches, welding the nickel to the cell tops.
I see no reason this would not work, but it obviously is cumbersome, and potentially increases risk of a mishap when laying down the sheet across a large pack.
2> attach both parallel and series connections with a high conductivity adhesive. Silver is much more conductive than nickel, so a silver based epoxy adhesive would provide strong, low r connections without welding or soldering.
It would actually be better than soldering, as solder is a piss poor conductor (which explains why people get mediocre results from overlaying a bus with solder.)
There are a wide number of such adhesives available.
Downside - they are expensive, and have a limited working time. you would have to be organized so that you don't waste it.
It also has limited shelf life. And you have to be careful what you select. There are formulations that are thermally conductive, but not particularly electrically conductive, which are packaged and sold right alongside the electrically conductive formulations.
https://www.amazon.com/Conductive-Adhesives-Adhesive-AA-DUCT-Syringe/dp/B00OSRNWOM/ref=sr_1_102?dchild=1&keywords=conductive+glue&qid=1620708797&sr=8-102#descriptionAndDetails
3> There is no 3.
Well, there is, but it's still germinating.
I was planning on putting together a 280 cell pack, but batteryhookup now has the spim08hp pouch cells cells broken out so it doesn't add $250 to ship them, so I cancelled my order for 18650's and I'm going pouch cells instead.
And it's not welding, soldering or any particular technology.
It's making a low resistance, chemically stable, vibration resistant connection by whatever means works.
So I thought of a couple alternatives:
1> Flip it - from what I understand (my welder is due for delivery today) while welding copper to nickel is a challenge, welding nickel to copper is trivial.
So if you're using cell holders, and your arrangement is symmetrical or mostly symmetrical, you could lay out your nickel parallel strips using the empty holders as a template, then lay your copper series strips with a slot or notch cut out, and weld the copper to the nickel.
Once the sheet is welded up, assemble the cells in the holders, flip the sheet and lay it on top and weld through the holes/notches, welding the nickel to the cell tops.
I see no reason this would not work, but it obviously is cumbersome, and potentially increases risk of a mishap when laying down the sheet across a large pack.
2> attach both parallel and series connections with a high conductivity adhesive. Silver is much more conductive than nickel, so a silver based epoxy adhesive would provide strong, low r connections without welding or soldering.
It would actually be better than soldering, as solder is a piss poor conductor (which explains why people get mediocre results from overlaying a bus with solder.)
There are a wide number of such adhesives available.
Downside - they are expensive, and have a limited working time. you would have to be organized so that you don't waste it.
It also has limited shelf life. And you have to be careful what you select. There are formulations that are thermally conductive, but not particularly electrically conductive, which are packaged and sold right alongside the electrically conductive formulations.
https://www.amazon.com/Conductive-Adhesives-Adhesive-AA-DUCT-Syringe/dp/B00OSRNWOM/ref=sr_1_102?dchild=1&keywords=conductive+glue&qid=1620708797&sr=8-102#descriptionAndDetails
3> There is no 3.
Well, there is, but it's still germinating.
I was planning on putting together a 280 cell pack, but batteryhookup now has the spim08hp pouch cells cells broken out so it doesn't add $250 to ship them, so I cancelled my order for 18650's and I'm going pouch cells instead.
NullValue said:
There are dozens of threads with discussion on all that.
The third option is mechanical pressure, as with magnets, poron foam "springs" etc
For this specific thread only one strategy is on topic.
Start your own thread for general discussion comparing others if you aren't able to find other existing ones to resurrect.
garolittle
10 kW
Advantages of pouch cells … Easier assembly. Disadvantage… Lower energy density than 18650 (usually).NullValue said:
spinningmagnets
100 TW
Discussion of compressing flat pouch cells has been moved to its own thread, found here:
"Compression of pouch cells, info/data"
https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=111797
"Index of flat pouch cell connection methods"
https://endless-sphere.com/forums/viewtopic.php?f=14&t=111704
"Compression of pouch cells, info/data"
https://www.endless-sphere.com/forums/viewtopic.php?f=14&t=111797
"Index of flat pouch cell connection methods"
https://endless-sphere.com/forums/viewtopic.php?f=14&t=111704
Hopefully using more than just two connection points.
The copper making the cell contact is much more reliable, the nickel just helping with the spotweld process.
Propulsion use cases inflict lots of shock/vibration, you don't want points of higher resistance causing hot spots current bottlenecks
The copper making the cell contact is much more reliable, the nickel just helping with the spotweld process.
Propulsion use cases inflict lots of shock/vibration, you don't want points of higher resistance causing hot spots current bottlenecks
TrotterBob
100 W
spinningmagnets said:
Getting a 404'ed from that link. Compression of pouch cells, info/data thread here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=111797
Scottyc said:Where did you find them?BigBlock said:dont' know if it has been discussed yet, but I found an interesting system that looks to avoid soldering the copper bus bar on the cell
Sent from my iPhone using Tapatalk
found the picture on Ali
garolittle
10 kW
3-minute video showing our pack connected with .25mm copper bus bars. Video also includes a discussion of the Sunstone Pulse Arc welder. Expensive machine but very good.
https://youtu.be/1Cy_MvvJtYg
https://youtu.be/1Cy_MvvJtYg
I've thought of soldering the copper to the nickel before welding to the cells. Could be as simple as single core copper onto 0.15 strip. I thought of using two off 5mm strips in parallel with copper along the outer edge then weld between them.BigBlock said:dont' know if it has been discussed yet, but I found an interesting system that looks to avoid soldering the copper bus bar on the cell
Hummina Shadeeba
10 MW
Just rip it off. Shouldnt damage the cell. I’ve never damaged any ripping off the nickel. dont slit your wrists by mistake.
_HeartGold
1 µW
- Joined
- Oct 4, 2016
- Messages
- 2
Has anyone tried plating 2.5 mm thick copper busbar with nickel, then spot-welding pure nickel strip to the battery cell and to the copper busbar? just curious. i see most people do the "sandwich" technique or use thin copper.
garolittle
10 kW
john61ct said:
Sunstone is awesome. I purchased their PA250i and I can spot weld .25mm thick pure copper directly to cylindrical lithium cells. See video link below…
https://youtu.be/1Cy_MvvJtYg
eMark
100 kW
PA250i Copper Battery Tab Welding System - Stylus & Weld Head Configuration and PAWH Weld Head designed for spot welding .25mm thick pure copper to li-ion cells ($37,500) ...
Apparently it takes a $19,500 PAWH pulse arc welder (shown below) in order to spot weld .25mm thick pure copper directly to cylindrical lithium cells ... https://www.accessotronik.com/product_p/supa250-ws_s489.htm
Apparently the conventional $10,829 Sunstone System (shown below) can't spot weld .25mm thick pure copper directly to cylindrical lithium cells as can garolittle's $19,500 Sunstone PA250i (shown above) ...
https://www.accessotronik.com/product_p/subws-h_s489.htm
Apparently it takes a $19,500 PAWH pulse arc welder (shown below) in order to spot weld .25mm thick pure copper directly to cylindrical lithium cells ... https://www.accessotronik.com/product_p/supa250-ws_s489.htm
Apparently the conventional $10,829 Sunstone System (shown below) can't spot weld .25mm thick pure copper directly to cylindrical lithium cells as can garolittle's $19,500 Sunstone PA250i (shown above) ...
https://www.accessotronik.com/product_p/subws-h_s489.htm
